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Optolong SII CCD 6.5nm Filter - 1.25" Mounted - SIICCD65-125
Optolong SII 6.5nm CCD Filter - 1.25”
The Optolong Sulfur II 6.5nm Extra Narrowband Filter transmits a 6.5nm bandwidth of light that is centered at 672nm and drastically reduces other transmissions, including wavelengths of light that are responsible for light pollution (both artificial and natural). Like all Optolong filters that are designated as “CCD”, this SII filter also blocks infrared wavelengths from 700nm to 1100nm so you don't need a separate IR-Cut filter.
The Optolong 6.5nm SII filter can be used in conjunction with H-Alpha and OIII filters for false color emission line images like the Hubble Space Telescope.
Due to the narrow bandwidth and high transmission rate of this filter, you will experience a major boost to contrast. The sky will be black, and when compared to a 12nm SII, half as many stars will peep through. Extra Narrowband filters work best with cameras that have very low dark current, but will allow you to image from sites with lots of light pollution.
The Optolong 1.25” SII 6.5nm Filter is made with Schott glass that has been multi-coated with an ion-assisted deposition technology to ensure scratch resistance and stability on the central wavelength, or CWL. The filter cell is made of lightweight, strong metal and is CNC machined, sand-blasted, black anodized, and then laser engraved. The result is a super thin filter cell that will produce a clear aperture of 26mm.
Quality Filter Materials:
- Schott B260 substrate material from Germany, 2.0mm thick
- CNC machined and black anodized aero-metal filter cell that is ultra-thin to provide largest clear aperture; Laser-engraved to prevent fading
- Multiple layers of anti-reflection non-cementing coatings applied via electron-beam gun evaporation with Ion-assisted deposition
Optolong Filter Manufacturing Processes and Parameters
- Filter substrate is fine-optically polished to 1/4 wave and <30 parallelism over both surfaces
- Surface quality, according to MIL-O-13830, is 60/40
- 80% transmission at SII line 672nm
- Infrared wavelength 700-1100nm cut-off
- 0.1% transmission Hg at 435nm and 578nm
- 0.1% transmission Na at 589nm
- High value transmission of pass-band and optical density of off-band is assured through Optolong’s planetary rotation system, a homogenous and precise coating procedure
- Thin metal cells have a clear aperture of 26mm for 1.25” filters
- Each filter comes with a plastic case with high pressure EVA case lining
Optolong is the Astronomy Filters division of Yulong Optics, an optical filter design and processing company out of Kunming, China that has provided filters for over 700 optical companies since 1999. All Optolong filters pass European Union RoHS requirements and have been certified by TUV Rheinland and Bureau Veritas.
Image shows the 12nm version of this SII filter rather than a 6.5nm, but they look very similar.